Launched in August 2013, Slack started as an internal communication tool utilized by small teams but has been rapidly morphing into a versatile communications platform used by many parties, including the open source community and large businesses.
Slack is a real-time messaging application that specializes in team communication. In a crowded space of productivity applications, Slack sets itself apart by providing extensive integrations with popular third-party apps and provides users with the platform to build their own integrations.
As of the beginning of 2016, Slack is used by approximately 2 million users daily, and spread across 60,000 teams that send 800 million messages per month (http://expandedramblings.com/index.php/slack-statistics/). Some of the more well known companies who use Slack include Airbnb, LinkedIn, and The New York Times. This service has become so popular, largely thanks to its impressive uptime rate of over 99.9 percent. What sets Slack apart from competition such as HipChat or Skype for Business is the determination of the company to open its platform for third-party developers in the form of an application program interface (API). To spur the growth of their service as a platform, in December 2015 Slack pledged to invest $80 million into software projects that use its technology (http://fortune.com/2015/12/15/slack-app-investment-fund/). Added to the more than $320 million raised in funding for the company, it's safe to say that Slack will continue to be a driving force in the team productivity space in the years to come.